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SGTC V2.0 - My Second Tesla Coil (UPDATED AGAIN)

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Sigurthr

Thu May 03 2012, 07:52AM

Registered Member #4463 Joined: Wed Apr 18 2012, 08:08AM
Location: MI's Upper Peninsula
Posts: 597

Okay! I finished the coil tonight! Man it was hard work but it came out nice! Tomorrow I fire her up for the first time and tune her up.

Note: NO HV points are touching any wood at all. I used Nylon 1/4-20 bolts and nuts for all HV connections and tie downs. There is a sheet of plexiglass under the primary, and the stationary primary lead (for the first turn) is inside a 1" PVC tube. The spark gap is now in a 2" section of 1" pvc tube for increased airflow and HV insulation. The HV terminal on the secondary is never routed inside the coilform to avoid interal arcs/streamers.

Primary is tapped at the predicted 13.0 turns. Up to 14.75 turns are supported. Topload is only resting on the top cap for easy removal. Secondary is removable for easy transportation/storage.

Picture:

Video: May I present: Sigurthr's SGTC V2.0 - YouTube

UPDATE: 5/3/12
I tested the coil today and found numerous pitfalls. What is clear to me now is that I am severed undercoupled and this coil requires more work. I will update the thread with all progress.

UPDATE: 5/4/12
It turns out the table I was working on has a steel plate under the wood and was sapping the inductance of my primary circuit, leading me to believe that the secondary had too much capacitance. I moved the coil inside and set it up on one of my wood only tables and it worked! I repaired/remade the primary tap with a better battery clamp and flexible stranded wire (the old one was 10ga solid and it broke from flexing) and put on a much smaller topload, and it tuned right up! I am quite happy with the coil now and feeling much better!

UPDATE: 5/14/12
I've made significant changes to the build and now achieving regular 18" streamers. Estimated output voltage 458kV.
Video:

brandon3055

Thu May 31 2012, 04:41AM

Registered Member #4548 Joined: Mon Apr 23 2012, 03:52AM
Location: tasmania
Posts: 271

Looks cool what are the specs?

Sigurthr

Fri Jun 01 2012, 10:24AM

Registered Member #4463 Joined: Wed Apr 18 2012, 08:08AM
Location: MI's Upper Peninsula
Posts: 597

Thanks!

Secondary: 18.5" of 30AWG HPN wire on a 4.5" dia form. hand wound 1/6" of a turn at a time, with no jig. (insanity)
Primary: 55 feet of 1/4" dia soft copper tubing - 6" ID, 25" OD, interturn spacing between 1/8" and 1/4", up to 14.75 turns.
Topload: 4" steel spheroid + breakout point
Tank Capacitors: 942C20S47K-F 0.01764uF x 16kV MMC
HV transformer: 7.5kV 30mA NST
Spark Gap: single stationary gap set to fire at 10kVp-p using two 1/4" brass sphere electrodes.
Quenching fan: Blower out of a $9 hair dryer. Powered by a 20VAC 10VA stepdown transformer.
All wires 14GA stranded or better.
All HV is isolated from the plywood base by plexiglass sheeting and nylon bolts.

It runs great now since the last change where I upgraded the wiring and fine tuned it. Regular streamers of 18" in length. There is some unfortunate breakout along the lead running from the final turn of the secondary to the topload, but I've mostly contained it with hot glue insulation. it looks ugly but helps performance. I'd love an alternative to fix the problem but I couldn't think of any. It even arcs under and around the hot glue a bit, but not very badly, it's just barely thicker than corona. Far better than it was without the hot glue.

Steve Conner

Fri Jun 01 2012, 10:45AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Sigurthr wrote ...

There is some unfortunate breakout along the lead running from the final turn of the secondary to the topload, but I've mostly contained it with hot glue insulation. it looks ugly but helps performance. I'd love an alternative to fix the problem but I couldn't think of any.

First of all congrats on your new coil! :)

To fix the unwanted breakout I suggest using a bigger topload that shields the top of the resonator better.

Insulation will only help to a certain extent. Eventually the high frequency corona will eat through it or set it on fire.

Sigurthr

Fri Jun 01 2012, 11:36AM

Registered Member #4463 Joined: Wed Apr 18 2012, 08:08AM
Location: MI's Upper Peninsula
Posts: 597

Hi Steve, thanks for the suggestion!
That is what I was afraid of, I went with such a small topload because I am at the edge of my tuning capability... 55feet of coil isn't enough if I were to move to a larger topload! I am tapped at 13 out of 14.75 possible turns on the primary. I had to solder on the outer 4.75 turns during post-production because it would not tune up even with no topload, the original design was for 10 turns but the secondary has way more capacitance than JavaTC and TeslaMap predicted.

So far the hot glue has held up to corona corrosion perfectly, but the PVC form has not. On the section of the wire where it breaks out, the HF tunnels underneath the hot glue making a (non-carbonized) channel in the PVC. In one section I managed to fully encapsulate the wire in hot glue which completely stopped breakout, but I couldn't do that to all the areas breaking out without risking a parial unwinding. The coil is polyurethaned, but not under the electrical tape which held the coil tight during coating. If I were to remove the hot glue from the area where it is breaking out I would also have to remove the electrical tape underneath it which is holding ~10turns in place. The wire there doesn't have missing insulation so it may be the ultimate fix but I'm a bit sqeamish about unwinding any of the coil, haha.

brandon3055

Fri Jun 01 2012, 01:42PM

Registered Member #4548 Joined: Mon Apr 23 2012, 03:52AM
Location: tasmania
Posts: 271

I don't now if it would fix your problem but this is how I terminated the ends of the primary on my SSTC

it also makes disasembly very fast and easy no nuts or bolts required

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